The invention relates to a cap for assembly onto a damper tube of a vibration damper, having an outer peripheral region which is cylindrical at least in sections, and at least one resilient spring tongue, wherein disposed on the spring tongue is at least one positive-locking element for producing a positive-locking connection between the cap and a protective element of the vibration damper.
German Patent Document DE 101 22 796 B4 discloses such a cap. The vibration damper described in this document includes a container tube in which a piston rod is guided in an axially movable manner, said piston rod being at least partially covered by a protective tube having at least one resilient fold. A stop buffer is disposed concentrically with respect to the piston rod, the stop buffer comes to lie against an end cap in an end region of a retracting movement of the piston rod. The end cap lies against the container tube in a completely assembled vibration damper. The stop buffer, the protective tube and the end cap form a preassembled structural unit independent of the vibration damper. The end cap is pressed against the container tube by the stop buffer when the piston rod undergoes a deflection movement into the container tube. For the purposes of connecting to the protective tube, the end cap comprises an edge that is circumferential at least in sections and is connected in a positive-locking manner to the protective tube. The end cap is designed to be radially resilient in the region of its edge. The container tube has a length section having a reduction in diameter in the direction of the end cap to be assembled.
A disadvantage in this known vibration damper is that the stop buffer, the protective tube and the end cap are to form a preassembled structural unit independent of the vibration damper. These components must thus be assembled to form a preassembled structural unit in a dedicated, separate working step, which requires a suitable tool in order to be able to achieve a uniform resilient deformation of the resilient segments of the end cap in order to be able to latch the protective tube with the end cap. In order to produce the positive-locking connection, a particular tool is thus required, which has to be separately obtained or produced. The assembly process is thus more complex and the production costs for the vibration damper are increased.
Exemplary embodiments of the present invention are directed to a vibration damper of the type mentioned in the introduction that can be assembled in a cost-effective manner by means of a simple assembly process.
In accordance with the invention, the at least one spring tongue comprises a region, which in the non-assembled state or in the delivery state of the cap, is set back radially inwards with respect to the outer peripheral region, wherein the set-back region comprises a spreading element by means of which the spring tongue is radially spread outwards when the cap is being assembled. By virtue of the region of the spring tongue that is radially set back with respect to the outer peripheral region, the positive-locking element is also radially set back to a position in which it cannot enter into a positive-locking connection with the protective element. Only when the cap is assembled on the damper tube is the spreading element actuated, which means that the spring tongue is spread radially outwards to such an extent that the positive-locking element moves into a position in which it enters a positive-locking connection with the protective element. Thus, the present invention does not require a particular tool for producing the positive-locking connection. The spreading element is actuated by the process of assembling the cap onto the damper tube, which is required in any case.
In accordance with a preferred embodiment of the invention, the cap is assembled by simply being slid onto the damper tube. The damper tube itself actuates the spreading element. The spreading element can be formed advantageously as an inclined surface or rounded section that is formed on the spring tongue of the cap. The inclined surface is preferably inclined radially inwards. Such an inclined surface or rounded section acts as a passive spreading element that co-operates with the damper tube when the cap is being assembled, i.e., no tool is required to spread the spring tongue radially outwards. The damper tube can have a constant diameter, in which case the spring tongues of the cap are adapted to the damper tube diameter. Alternatively, the damper tube can have a diameter enlargement, which means that only the larger diameter co-operates with the spreading element. This latter embodiment is described in more detail hereinafter during the description of a specific exemplified embodiment. The basic assembly process is the same for both of the aforementioned variations, i.e., regardless of whether the damper tube has a constant diameter or a diameter enlargement.
In accordance with exemplary embodiments of the present invention, the cap comprises several spring tongues that are disposed distributed over the circumference of the cap. In a particularly preferred manner, three spring tongues are provided distributed at regular intervals over the circumference of the cap. This ensures a reliable positive-locking connection between the cap and the protective element.
In accordance with a structurally simple embodiment of the invention, the positive-locking element is formed as an integral component of the spring tongue. For instance, the positive-locking element can be formed as a latching lug attached to or integrally formed on the spring tongue. The positive-locking element engages into a corresponding recess in the protective element in the assembled state of the cap so that that these two components are connected together in a positive-locking manner.
In an advantageous manner, the cap comprises a stop surface for positioning the protective element by means of which the protective element can be positioned relative to the positive-locking element in a position suitable for forming the positive-locking connection. The protective element lies against the stop surface in the assembled position. The stop surface is disposed on the cap such that a receptacle, provided on the protective element, for the positive-locking element is positioned relative thereto such that the positive-locking element penetrates radially outwards into the receptacle by virtue of the spreading action of the spring tongue produced when the cap is assembled. In this manner, the protective element is readily aligned into the correct position for forming the positive-locking connection. In accordance with a preferred embodiment of the invention, the stop surface is formed as a circular ring-shaped surface in order to reliably and effectively position the protective element relative to the cap.